Panama City, Panama CNN  — 

Pope Francis has taken another shot at wall-building politicians, telling thousands of Catholics in Panama gathered for World Youth Day that “builders of walls sow fear” and “divide people.”

“We know that the father of lies, the devil, prefers a community divided and bickering,” Francis told a crowd of tens of thousands of youth Thursday night at a seaside park in Panama City.

“This is the criteria to divide people: The builders of bridges and the builders of walls, those builders of walls sow fear and look to divide people. What do you want to be?”

When the crowd replied “builders of bridges,” Francis replied, “You learned well. I like that.”

The Pope’s remarks seemed to be a clear reference to President Donald Trump’s proposal to build a wall along the US-Mexico border. Trump’s demand for $5.7 billion for the wall has led to a partial government shutdown for 34 days and counting.

On Wednesday, after Trump tweeted a new slogan, “Build a wall and crime will fall,” a journalist on the papal plane asked Pope Francis about Trump’s proposal. The Pope said such measures are driven by fear. “It is the fear that makes us crazy.”

It wasn’t the first time Trump and Francis have tussled over the proposed border wall.

“A person who thinks only about building walls, wherever they may be, and not building bridges, is not Christian,” Francis said in 2016. “This is not the gospel.”

Trump immediately fired back, calling Francis’ comments “disgraceful.”

“No leader, especially a religious leader, should have the right to question another man’s religion or faith,” he said in a statement.

Pope visiting youth prison

World Youth Day continues until Sunday. Despite the shadow of controversy because of the clergy sexual abuse crisis, the trip is a coming home of sorts for Pope Francis, the first Latin American pontiff.

According to the Vatican, about 150,000 youth have enrolled so far, a much lower turnout than World Youth Days in 2013 in Rio de Janeiro and in 2016 in Krakow, Poland, which attracted about 3 million each.

During his speeches on his five-day trip to Panama, the Pope has repeatedly criticized the use of fear as a driver of divisions and the creator of an us-versus-them mentality.

On Thursday, Francis, the son of Italian immigrants, said that “forced migration,” driven by violence and poverty, is thrusting young migrants to leave everything behind and take a perilous journey for safer ground.

“They find themselves boxed in and lacking opportunities, amid highly confidential situations with no quick solution: domestic violence, the killing of women – our continent is experiencing a plague in this regard – armed gangs and criminals, drug trafficking and sexual exploitation of minors and young people,” Francis said to a gathering of Central American bishops in Panama.

Overcoming these fears, he said, will require the church to do more than just welcome immigrants. Instead, he instructed his bishops to create dialogue “to help overcome fears and suspicions” that live in the imaginations of people.

On Friday, Francis visited to a youth detention center in Panama, where he warned that division creates an “invisible wall.”

“This attitude spoils everything, because it erects an invisible wall that makes people think that, if we marginalize, separate and isolate others, all our problems will magically be solved,” Francis said.

Instead of backbiting and fighting on the issue, which the Pope says is a cycle society can fall into, Francis said communities should work to “create opportunities and change.”